The invention is directed to a hermetically and tightly sealed optical transmission module having one or more semiconductor lasers arranged on a carrier body, an optical fiber for each laser leading away from the body with a hermetically tight optical connection on the body for each laser and the respective optical fiber.
A transmission module of said species is disclosed by M. Yano and K. Vakao, xe2x80x9cOptical Semiconductor Devices and Modules for Optical Parallel Link,xe2x80x9d Fujitsu, Sci. Tech. J. 30, 2, pages 195-202 (December 1994). In this known module, the hermetically tight, optical connection between each semiconductor laser and the optical fiber optically connected thereto is comprised therein that the fiber is soldered into the carrier member and an end face of this soldered-in fiber lies immediately opposite a light exit window of the semiconductor laser.
The carrier member itself is composed of two body sections, the fibers being soldered into the one thereof and the semiconductor lasers being secured on the other. The two body halves are connected to one another such that the end face of a respective fiber is arranged opposite the light exit window of each semiconductor laser.
S. Hanatani et al, xe2x80x9c10 Channel Fully-integrated High-Speed Optical Transmitter Module with a Through-put Larger Than 8 bitsxe2x80x9d, Proc. 21st ECOC ""95, Paper ThB.1.4, pages 875-878, discloses an optical transmission module, whereby a plurality of semiconductor lasers are arranged in a cavity of a housing, whereby each semiconductor laser is optically connected to an optical fiber leading away from the housing, being optically connected thereto by a planar micro-lens secured in the housing. A plurality of electrical connecting lines for producing an electrical connection between the cavity and the outside environment of the housing are also secured in the housing.
The housing is composed of a first housing section that comprises a sack-like recess defining the cavity in which all semiconductor lasers are arranged and in which electrical connecting lines are secured, and is composed of a second housing section in which the planar micro-lens to which the fibers are connected is secured.
For producing the optical connection between the semiconductor lasers and the fibers, the second housing section is plugged into an opening of the sack-like recess of the first housing section.
The invention has the advantage that a hermetically tight or sealed transmission module is offered that is fabrication-friendly to manufacture.
In particular, the inventive module has the advantage that an extremely fabrication-intensive metallization and soldering of fibers into a housing or a housing section is not required. A polishing as well as an anti-blooming of fibers secured in a housing are also advantageously eliminated. The risk of breakage of fibers that have been soldered in at the solder location advantageously does not exist.
Advantageously, the inventive module can be particularly utilized as a hermetically tight or sealed transmission module for parallel optical links that are gaining in significance in the immediate future as cost-beneficial and performance-capable transmission means for data rates of approximately 100 Mbit/s through 2.5 Gbit/s per channel and transmission distances from approximately 1 m up to approximately 10 km. The applied potential of such links extends from optical backplanes or, respectively, backplane wirings, for example for high-performance telecom switching systems via computer connections to LAN backbones and the subscriber terminal area.
Such links are essentially composed of the transmission module, which is usually composed of a laser line with suitable electrical inputs and optical outputs and a fiber ribbon cable as transmission medium, as well as of a receiver module having optical inputs and electrical outputs.
Dependent on the area of employment, different technologies, or, respectively, sub-components are thereby utilized, for example short-wave lasers such as VCSL or Fabry-Perot lasers and multimode fibers for short transmission distances or long-wave Fabry-Perot lasers or DFB lasers as well and monomode fibers for longer transmission distances and high data rates. The coupling of the fibers to the semiconductor lasers in the transmission module is thereby especially difficult and cost-intensive, particularly when monomode optical fibers are to be utilized and when a hermetically tight embodiment is required for dependability reasons.
The inventive module advantageously satisfies these demands.
In order to govern the adjustment tolerances better when coupling the semiconductor lasers to the monomode fibers and, thus, to govern the manufacturing costs similar to the known module of the species initially cited, a simple butt coupling is utilized in the inventive module and a spot matching realized, for example, by optical lenses between the semiconductor lasers and the fibers as standard in telecom modules for high data rates up to 10 Gbit/s and long transmission distances of, typically, at least 50 km is foregone.
The lower coupling efficiency of approximately xe2x88x9210 dB compared to, typically, xe2x88x926 through xe2x88x922 dB given spot matching that is involved with the butt coupling can be advantageously accepted because of the shorter transmission distances and, moreover, the lower coupling efficiency advantageously leads to lower reactance of reflections onto the semiconductor laser, this being important for data rates above 622 Mbit/s given transmission distances of several kilometers since, by contrast to the high-end telecom modules, no optical insulators are utilized. As a result of employing butt coupling, the problems involved with lenses, for example complicated manufacture and adjustment problems also do not occur.
A very particular advantage of the inventive module is to be seen therein that a hermetically tight module design that is otherwise especially difficult to realize is offered that can be realized in a relatively simple, fabrication-friendly and cost-beneficial way.
The inventive module differs from the known module with butt coupling of the species initially cited essentially in that
the carrier member is composed of a housing that hermetically tightly surrounds a cavity in which the semiconductor laser or lasers are arranged; in that
a hermetically tight optical connection between a semiconductor laser and an optical fiber is not realized, as in the known arrangement, by a hermetically tight fastening by soldering the fiber itself in the housing but is realized with a separate, optical connecting waveguide secured hermetically tight in the housing for producing an optical connection between the cavity and the outside environment of the housing; and in that
a housing is realized with one or more electrical lines secured hermetically tight in the housing for producing an electrical connection between the cavity and the outside environment of the housing.
As a result of the inventive connecting waveguide, a difficult and complicated manipulation of the fiber end sections during metallization, soldering, polishing end faces and anti-blooming is illuminated, as is a risk of breakage of the fibers due to the solder locations.
Given the module of the second-sided document, the semiconductor lasers are in fact arranged in a cavity of a housing in which electrical connecting waveguides are secured for connecting the cavity and the outside environment of the housing; however, the fibers are not connected by inventive connecting waveguides and simple butt coupling but are optically connected to the semiconductor lasers by a planar micro-lens.
The invention is described in greater detail by way of example in the following specification with reference to Figures.